The present invention relates to an improved valve train for an internal combustion engine, and more particularly, to a valve deactivator assembly for use therein.
Although the valve deactivator assembly of the present invention may be utilized to introduce some additional lash into the valve train, such that the valves open and close by an amount less than normal, the invention is especially suited for introducing into the valve train sufficient lash (also referred hereinafter as "lost motion"), such that the valves no longer open and close at all, and the invention will be described in connection therewith.
Valve deactivators of the general type to which the invention relates are known, especially in connection with internal combustion engines having push rod type valve train in which there is a rocker arm, with one end of the rocker arm engaging a push rod, and the other end engaging the engine poppet valve. Typically, a central portion of the rocker arm is fixed relative to the cylinder head (or other suitable structure) by a fulcrum arrangement, as is well known to those skilled in the art, in which the fulcrum normally prevents movement of the central portion of the rocker arm in an "up and down" direction, while permitting the rocker arm to engage in cyclical, pivotal movement, in response to the cyclical motion of the push rod, which results from the engagement of the push rod with the lobes of the rotating camshaft.
Examples of known valve deactivator assemblies are shown and described in U.S. Pat. Nos. 4,221,199; 4,256,070; 4,305,356; and 4,380,219, all of which are assigned to the assignee of the present invention, and incorporated herein by reference. The valve deactivators of the above incorporated patents have typically involved some sort of latch member which is movable (typically, rotatable, but in some cases, movable linearly) between a latched position and an unlatched position. The movement of the latch member conventionally occurs is response to linear movement of a linear actuator, by means of an appropriate linkage arrangement.
Although the prior art valve deactivators have operated in a generally satisfactory manner, the actuator arrangement, including the required linkage, has resulted in an unacceptably slow response time, thus limiting the ability of the arrangement to be operated by the engine microprocessor, in synchronism with various other engine systems. The prior art devices typically had a response time, from "ON" to "OFF", or vice versa, in the range of about 100 to 200 milliseconds
In modern internal combustion engines, utilizing fuel injection, it is especially desirable in a valve deactivator system to turn off the fuel injectors at the same time that the operation of the valves is stopped. However, the fuel injectors are electrically actuated, and can be turned off almost instantaneously, and therefore, it is desirable to be able to activate the valves and turn on the fuel injectors, or deactivate the valves and turn off the fuel injectors, within the ensuing, single revolution of the engine camshaft. Thus, and by way of example only, in developing the present invention, the goal for the valve deactivator system was a maximum time of less than 25 milliseconds from "ON" to "OFF", or vice versa.
The actuator and linkage arrangements used in the prior art devices have resulted in an excessive number of parts, increasing the overall cost of the system. Finally, the actuator and linkage arrangements have typically taken up enough space to limit the packaging options in the engine cylinder head. This has been especially true in the valve deactivator arrangements of the type shown in the above-incorporated patents wherein the deactivator mechanism comprises part of the fulcrum arrangement of the rocker arm. In a conventional "center-pivot" rocker arm for use with a push rod arrangement, the fulcrum arrangement would typically be disposed entirely within the profile of the rocker arm. However, adding a valve deactivator mechanism to the fulcrum arrangement would cause the fulcrum arrangement to extend substantially above the profile of the rocker arm, thus substantially altering the overall configuration of the cylinder head.